Longitudinal outcomes among patients with fibromyalgia, chronic widespread pain, or localized chronic low back pain.

Objectives: The objective of this study was to compare longitudinal outcomes of patients with FM, CWP, or localized chronic low back pain (LBP) to determine whether FM is an extreme manifestation of the CWP continuum.

Methods: A retrospective cohort study was conducted within a national pain research registry from August 2019 to July 2023. A total of 310 participants with FM (and CWP), CWP (without FM), or LBP were followed for 12 months to measure pain intensity, back-related disability, and health-related quality of life (HRQOL). Multivariable analyses were performed with generalized estimating equations (GEEs), including baseline and longitudinal covariates to adjust for potential confounding.

Results: The mean age of the participants was 52.3 (standard deviation [SD], 13.6) years, and 238 (76.8 %) were female. There were 64 (20.6 %) participants with FM, 56 (18.1 %) with CWP, and 190 (61.3 %) with LBP. There were no differences in pain intensity among the groups. Compared with back-related disability in the LBP group (mean, 12,7; 95 % confidence interval [CI], 11.4-14.1), the FM group (mean, 15.3; 95 % CI, 13.7-17.0; p=0.006) and CWP group (mean, 16.2; 95 % CI, 14.8-17.7; p<0.001) had greater disability. There were no clinically relevant differences in pain and disability between the FM and CWP groups. Compared with the LBP group, the FM group had worse outcomes on five HRQOL scales, and the CWP group had worse outcomes on all seven scales. Clinically relevant HRQOL differences between the FM and CWP groups involved anxiety and depression, with results favoring the FM group.

Conclusions: These findings do not support the view that FM is an extreme manifestation of the CWP continuum, involving greater pain, disability, or HRQOL deficits.